This invention relates to a control for an electric motor-operated vehicle, and more particularly to an improved control that allows regenerative braking and a control for such regenerative braking.
The use of electric motors for providing either the primary motive power or auxiliary, assist motive power for a wide variety of vehicles have been proposed. It has been acknowledged that in such vehicles, the electric motor may also be employed as a way of obtaining a braking effect for the vehicle. Since the motor will be driven when the vehicle is being decelerated and electric power is not being supplied to the motor, it can be utilized as a generator and this generating effect can be utilized for regenerative braking. Thus, many vehicles having such electric motor propulsion systems also employ regenerative braking.
Normally, the regenerative braking system requires some operator input for actuating the braking mechanism. It may be desirable, however, to provide that the regenerative braking is automatically applied under a wide variety of different types of circumstances.
It is, therefore, a principal object of this invention to provide an improved electric motor propulsion system for a vehicle that employs regenerative braking and wherein the braking effect is automatically applied in response to certain conditions.
It is a further object of this invention to provide an improved electric motor control for an electric motor driven vehicle wherein the system employs a regenerative braking system that is automatically applied in the event of some failure in the control system so as to bring the vehicle to a halt.
One difficulty in connection with the use of regenerative braking in electric motor powered vehicles is that the vehicle then becomes difficult to push manually. It is frequently the situation where the electric motor propulsion, be at either of the full power or of the assist power type, is employed in a vehicle that may be manually pushed. For example, this type of propulsion system is frequently utilized in vehicles such as bicycles, wheelchairs, or other small vehicles that may, from time to time, require manual pushing. The drag caused by the regenerative braking can, however, cause difficulty in pushing the vehicle.
It is, therefore, a still further object of this invention to provide an improved electric motor control system for an electric power driven vehicle that embodies regenerative braking and wherein the braking system is disabled automatically during conditions when the vehicle may be desired to be pushed.
This result can be achieved by providing a clutch mechanism between the driving motor and the propulsion device of the vehicle. However, when this is done, then the operator need disengage the clutch in order to facilitate the pushing operation. If the vehicle is of the wheelchair type, there may be a separate motor for each driving wheel and thus there will be required a clutch and operator for each wheel. This is obviously not only disadvantageous and inconvenient, but adds to the cost.
It is, therefore, a still further object to this invention to provide an improved control system for an electric motor driven vehicle having a regenerative braking system wherein the braking system is automatically disabled under conditions when the vehicle may be pushed so as to avoid the necessity of utilizing a clutch in the transmission between the motor and the vehicle propulsion device.
As has been noted, it may be desirable employ an arrangement wherein the regenerative braking system is automatically engaged in response to some sense condition such as a failure in the control circuit. Where this is done, however, once the vehicle is stopped it also may be necessary or desirable to push it. If the regenerative braking system is engaged under the aforenoted condition, then the pushing again may be difficult.
It is, therefore, a still further object of this invention to provide an improved electric motor control for an electric motor power vehicle wherein there is provide a regenerative braking system that is automatically engaged for braking the vehicle in response to a sensed condition and wherein the regenerative braking system is disabled once the vehicle has stopped so as to facilitate its pushing.